The invention relates to an open-end friction spinning machine having a plurality of spinning units, each containing two rollers arranged next to one another and drivable in the same rotational direction. The two rollers are positioned so as to form a wedge-shaped gap in which, by means of a friction effect, yarn is formed from individual fibers fed to the gap. At least one roller is equipped with a suction insert connected to a vacuum source.
A primary objective of the invention is to design an open-end friction spinning machine of the above-mentioned type in such a way that the quality of the yarn spun at each individual spinning unit, as well as the relative quality among spinning units, is kept as uniform as possible throughout the duration of the operating time.
This objective is achieved in that means are provided for monitoring at least a part of the friction effect.
The invention is in this case based on the knowledge that spinning conditions and, thus, the yarn produced, are very dependent on the friction effect which is primarily affected by the coefficient of friction of the surfaces of the rollers and the vacuum of the suction insert or inserts acting in the wedge-shaped gap. Changes of this friction effect will immediately result in a change of the quality of the yarn and the structure of the yarn. By monitoring the friction effect according to the invention, it becomes possible to recognize these changes early and to take appropriate countermeasures so that a uniform quality of yarn can be maintained.
In order to be able to counteract the changing friction effect, means are provided in an advantageous aspect of the invention for adjusting at least part of the friction effect.
In a further development of the invention, means are provided for stopping a spinning unit which are controlled by the means used for the monitoring. The stopping prevents qualitatively useless yarn from being wound unto a spool. However, stopping will, as a rule, be useful only if the changes determined by monitoring are such that they cannot be eliminated simply by means for adjusting the friction effect.
In a first embodiment of the invention, each spinning unit is equipped with at least one vacuum supply means connected to a signal transmitter and/or to a device for stopping the spinning unit. Through these devices, that part of the friction effect is controlled that is caused by the suction insert or inserts. When the changes are so great that a qualitatively useless yarn is produced, it is advantageous to stop the problem spinning unit. However, when the changes are noticeable but do not result in an unacceptable lessening of the quality of the yarn, an operator or a servicing apparatus can be called via the then actuated signal transmitter for the purpose of carrying out an examination or an adjustment. It is advantageous to provide each spinning unit with a control valve having an adjusting element in the connection to the suction insert or inserts. Thus the desired vacuum can then be adjusted individually at the corresponding spinning unit.
In another advantageous aspect of the invention, the vacuum supply means of the spinning units is connected to a central evaluating circuit controlling means for adjusting the vacuum at an individual spinning unit and/or to means for interrupting the spinning operation of the individual spinning units. By means of this development, continuous monitoring of the individual spinning units is made possible. This, however, requires relatively high manufacturing expenditures.
In a further development of the invention, the means for monitoring and adjusting at least part of the friction effect of the rollers of a spinning unit and the means for stopping and/or marking a spinning unit are housed in a servicing apparatus that can be moved along the machine and applied to an individual spinning unit. In the case of this development of the invention, the necessary expenditures can be reduced considerably, but only a periodic monitoring of the individual spinning units is possible. Such periodic monitoring would be sufficient in a majority of cases because changes in the friction effect take place only after a certain length of operating time.
In a further development of the invention, means are provided for detecting the part of the friction effect of a spinning unit that is caused by the coefficient of friction of the surfaces of the rollers. This makes it possible to detect a significant part of the friction effect. The combination of monitoring of the vacuum and of detecting the coefficient of friction results in particularly reliable monitoring. The change of the coefficient of friction of the surfaces of the rollers can take place as the result of deposits but also as a result of wear of the surface structure of the rollers.
In an advantageous development, means for conditioning the surfaces of the rollers are provided which are controlled by the means for detecting the coefficient of friction of the surfaces. These means for conditioning, which may cause cleaning and/or treating and/or coating of the surfaces of the rollers, have the purpose of restoring the desired surface structure and, thus, the desired coefficients of friction. In this manner, uniform spinning conditions are maintained.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.